WO2013160103A2

WO2013160103A2 - Strand anchor

Info

Publication number: WO2013160103A2
Application number: PCT/EP2013/057444
Authority: WO
Inventors: Frank Schmidt
Original assignee: Hilti Aktiengesellschaft
Priority date: 2012-04-23
Filing date: 2013-04-10
Publication date: 2013-10-31
Also published as: DE102012206613A1; WO2013160103A3

Abstract

The invention relates to a strand anchor, in particular for use in mining, comprising a supporting member, which comprises a plurality of wires, and an anchor head, which is arranged on the supporting member. The invention provides that only some of the wires of the supporting member extend as far as the anchor head, whereas the rest of the wires of the supporting member terminate before the anchor head.

Description

Strand

DESCRIPTION

The present invention relates to a strand anchor according to the preamble of claim 1.

In mining, tunneling and special civil engineering strand anchors are used to prevent rock movements of the upcoming rock, to slow down or to prevent larger flaking of pending rock and thus to allow safe operation. The strand anchor is cohesively with a hardenable mass, z. As mortar or synthetic resin, fixed in a hole on the upcoming rock. After incorporating a borehole into the rock, cartridges of hardenable mass can be introduced into the borehole. Subsequently, the strand of the strand anchor is inserted into the borehole, which destroys the cartridges and mixes their contents. US 2010/0189515 A1 and US 2010/0290841 A1 show a tensioning device for cables.

DE 295 21 197 U1 shows an anchor element for a temporary press anchor from a bundle of individual tension members, which are embedded in the area of the composite length in a press body and are individually cased in the area of the free steel length. The individual tension members are made of steel rods which, at least in the region of the composite length, have force lines running helically and forming at least a partial bundle. Transmission ribs are provided and the individual members are surrounded in the region of the composite length of closed on the top, thin-walled sheaths, the wall of which is profiled in the thread of the steel bars and the individual composite lengths of Einzelzugglieder are staggered over the entire composite length of the anchor element that they are not or only to overlap by a small length. The individual tension members as steel rods are thus surrounded by cladding tubes.

The object of the present invention is to provide a particularly simple and inexpensive and at the same time load-bearing and reliable strand anchor.

This object is achieved with a strand anchor with the features of claim 1. Preferred embodiments are given in the dependent claims.

Accordingly, in a strand anchor, in particular for use in mining, comprising a support member comprising a plurality of wires and arranged on the support member anchor head, provided that only a part of all the wires of the support member reaches to the anchor head, whereas the other part of the wires of the support member before Anchor head ends.

The invention has recognized that in vollverklebten anchors, ie anchors in which the hardenable mass ranges from the bottom of the hole to the borehole mouth, only a part, typically about 20 to 50%, of the maximum anchor force is entered into the anchor head. For most of the load is already introduced via the bond to the upcoming rock, which is caused by the hardened mass, previously in the rock. Based on this finding, the invention proposes to lead only a portion of the wires of the support member to the anchor head, while the other part ends in front of the anchor head and thus does not reach to the anchor head. Since only a fraction of the maximum anchor force acts in the area of the anchor head, this is possible without any loss of payload. The comparatively small number of wires in the area of the anchor head, ie in particular the Equally compact design of the strand, it makes it possible to construct the anchor head comparatively easy, since the armature head only comparatively few wires must be kept. However, since the anchor head represents a relatively complex element in the overall construction of the Litzenan- kers, thus a particularly simple and at the same time sustainable anchor can be obtained.

According to the invention, it is accordingly provided that, by varying the steel cross-section of the support member along the support member, only part of the total cross-section is guided to the anchor head, thus enabling a simpler and more compact anchor head construction. This proportion of the steel cross-section usually has to be at least as large as the percentage of the anchor force that has to be transmitted to the anchor head. A pretensioning force can also be applied via the part of the total steel cross section that leads to the anchor head. The already before the anchor head (ie in the borehole) ending shares of the total steel cross section are only by the additional load bearing of the armature, so e.g. by ground deformations, loaded and thus take a considerable part of the anchor load, especially in the areas in which the armature is subjected to high normal forces. By virtue of the relatively soft composite anchorage of the part of the total steel cross section ending in the borehole, its load fraction continuously decreases until its end. This proportion of load is transmitted to the surrounding subsoil (ground, rock) or to the part of the total cross section up to the anchor head.

It is particularly preferred that the wires that end in front of the anchor head, which do not extend to the anchor head and which are spaced from the anchor head, have a different surface finish and / or a different diameter than the wires that extend to the anchor head. In particular, the part of the wires ending in the borehole can be designed for a particularly good bond to the hardened mass, since these wires do not have to be bordered on the anchor head, and since it is thus, for example the compression behavior of a bundle of these wires often does not matter. The wires that do not extend to the anchor head, therefore, may, for example, have a surface profiling that improves the interaction with the surrounding mass. In particular, thus, the run up to the anchor head part of the support member can be made particularly well tensioned to effectively clamp the anchor head against the rock can, and lying completely in the hole, that is, the spaced from the anchor head part, can be designed for a particularly high composite be to well after the borehole injection, the individual layers stick together.

In one embodiment of the invention, the support member may be a stranded wire. As a result, a particularly easy to handle anchor is provided. A strand can be characterized in particular in that its respectively adjacent wires abut each other directly and / or that their wires are intertwined. In the case that a strand is provided as a support member, only a portion of all the wires of the strand reaches to the anchor head, whereas the other part of the wires of the strand terminates in front of the anchor head.

In an alternative embodiment, the support member consists of a central strand and a plurality of individual wires which surround the strand, preferably at a distance, preferably the wires of the strand extend to the anchor head and at least a portion of the individual wires, in particular all individual wires before Anchor head ends. According to this embodiment, the central strand is guided to the anchor head, while the outer individual wires can be formed composite optimized. As a result, the load capacity can be further increased. The individual wires can be connected via spacers with the strand and / or with each other. In particular, the individual wires and the strand can be arranged concentrically.

In a further alternative embodiment, the support member consists of, in particular parallel, individual wires, which are preferably connected to one another via a spacer, wherein only a part of all individual wires wires to the anchor head is sufficient, whereas the other part of the individual wires ends in front of the anchor head. This can be advantageous in terms of manufacturing costs. In a further embodiment it can be provided that the support member has two strands, wherein the first strand extends to the anchor head, whereas the second strand terminates in front of the anchor head. Such an anchor can be made particularly simple. The two strands are preferably connected to one another via one or more spacers and / or extend at least in sections parallel to one another. In particular, the two strands can be of the same type. Preferably, they can thus have the same number of wires and / or the same cross-section. In this embodiment, therefore, preferably two identical strands can be pushed parallel into the borehole, wherein only one of the strands protrudes from the borehole.

It is particularly preferred that the anchor head has an anchor nut for biasing the support member. This anchor nut is adjustable along the support member. Accordingly, the strand anchor can be prestressed, but the prestressing level in the mining sector can be relatively low in comparison to the overall load and, for example, can be approximately 10 to 30% of the total load. The anchor head can for example have a fixing part for the support member in which the support member is fixed axially, for example, is keyed, and which has a thread on which the anchor nut is arranged. The anchor head can also have an anchor plate for resting on the rock, wherein the wires extending to the anchor head preferably extend through the anchor plate.

In particular, it can be provided that the strand and / or the individual wires are not enclosed by a hollow tube, so that a direct contact between the hardenable mass and the strands or the individual wires can be produced. In the direction of the longitudinal axis of the support member, a different number of wires or different sums of cross-sectional areas of the wires are present. This allows a local Passing be realized to be absorbed by the support member tensile forces. Since the greatest tensile forces generally occur centrally in the direction of the longitudinal axis, the largest sum of wire cross-sectional areas and / or the largest number of wires can be present here. At a front end portion facing the anchor head, but also at a rear end portion of the support member facing away from the anchor head, generally lower tensile forces are to be absorbed by the wires, so that in the front, but possibly also in the rear portion, only a smaller sum may be present on a wire cross-sectional area and / or a smaller number of wires for receiving the tensile forces.

Preferably, a maximum of 30%, 50% or 70% of the wires to the anchor head and / or the distance of the wires do not extend to the anchor head, the anchor head is at least 5%, 10% or 20% of the total length of the support member.

In a supplementary variant, at least one longitudinal channel, preferably a plurality of longitudinal channels, is formed between the wires, through which air can be diverted to the outside upon introduction of hardenable mass into the borehole.

The invention also encompasses an arrangement consisting of a substrate with a borehole in which a strand anchor according to the invention is accommodated and adhesively bonded to the substrate by means of a hardened mass, wherein the hardened mass preferably extends to the borehole mouth of the borehole.

The invention further relates to a method for attaching a strand anchor, in particular a strand anchor described in this patent application, comprising the steps of: incorporating a wellbore in rock, inserting a multi-wire support member into the wellbore, introducing hardenable mass into the wellbore, the strand anchor is introduced such that a front end of a first part of the wires is outside the borehole and a front end of a second part the wires lies within the borehole. Only a portion of the wires terminate outside the borehole. This first part of the wires can be used to bias the strand anchor. The first and the second part of the wires of the strand anchor are used for bonding to the hardenable mass. The strand anchor can be made very simple, because only the first part, ie, a relatively small number of wires, is to be accommodated on a fixing part for prestressing the strand anchor.

In particular, the air displaced by the hardenable mass from the borehole is at least partially, in particular completely, discharged out of the borehole through at least one longitudinal channel, preferably a plurality of longitudinal channels, in the support member. An injecting or venting line can thus be eliminated in an advantageous manner. In a further embodiment, the wires are formed in cross-section substantially circular. Preferably, the strand anchor comprises a plurality of spacers for the individual wires. Between the spacers, the individual wires, preferably continuously, can have a substantially constant distance from the strand or rest on the strand between the spacers. In a variant, the individual wires are arranged at a distance from the strand. In a further embodiment, the spacer made of metal or plastic. In an additional embodiment, the wires of the strand and / or the individual wires are at least partially, in particular completely, made of metal, in particular steel.

In an additional embodiment, at least a portion of the wires, in particular the part that ends in front of the anchor head, on the outside of an embossing or profiling on. As a result, the mechanical bond or the cohesive connection with the hardenable mass can be increased.

In particular, after hardening the hardenable mass, for. As mortar or synthetic resin, a tensile force applied to the support member with the anchor nut. The anchor nut is used to point at the rock in the area of the borehole munds applied a compressive force. As a result, the outer rock layers are secured and the compressive force is introduced as a tensile force in the support member and cohesively transferred from the support member with the hardened mass on the rock in the region of the borehole.

Hereinafter, embodiments of the invention will be described in more detail with reference to the accompanying drawings. Show it:

1 shows a longitudinal section of a strand anchor in a first embodiment, which is inserted into a bore in rock, wherein hardenable mass is introduced into the space between the rock and the anchor tube, a cross section AA according to FIG. 1 of the strand anchor, a longitudinal section of the strand anchor in a second embodiment, which is inserted into a hole in rock, wherein hardenable mass is introduced into the space between the rock and the anchor tube, a diagram with the abscissa plotted length of the support member beginning with the outermost front end and on Anchor force applied to the ordinate, Fig. 5 is a graph with the abscissa plotted on the

Fig. 6 shows a further embodiment of an anchor head with a fixing part, an anchor nut and an anchor plate, and starting from the outermost front end and the ordinate applied sum of the cross-sectional areas of the wires or the number of wires

Fig. 7 shows another embodiment of a strand anchor in longitudinal section. A Strand Anchor 1 is used in mining for the temporary securing of rock 18 on tunnels or in special civil engineering to secure ground. The strand anchor 1 has an anchor head 101 to which a support member 100 is attached with a plurality of wires. The strand anchor 1 is a chemical anchor, ie that the support member 100 with a hardenable mass 1 1, z. As resin or mortar, is firmly bonded in the rock 18. For this purpose, a borehole 19 is to be worked into the rock 18 and subsequently the support member 100 and the hardenable mass 11 are introduced into the borehole 19.

In the first embodiment, the support member 100 comprises a stranded wire 2 of a plurality of wires 3 made of steel and additionally also seven individual wires 7 made of steel. The wires 3 of the strand 2 have different diameters in the illustrated embodiment. In principle, however, all the wires 3 of the strand 2 can have the same diameter. The individual wires 7 are formed by a plurality of annular spacers 8, e.g. made of plastic, spaced from the strand 2 held as a central strand. According to the representation in FIG. 1 as the first exemplary embodiment of the stranded anchor 1, the individual wires 7 have a substantially constant distance from the stranded wire 2, so that the individual wires 7 do not touch the stranded wire 2.

The support member 100 has a rear end 5 which faces the borehole bottom of the borehole 19. On the opposite side, the wires 3 of the strand 2 and the individual wires 7 are led out of the borehole 19 to different extents. The individual wires 7 lie entirely in the borehole 19, so that the individual wires 7 are completely enclosed by the mass 11, ie the front ones Ends 6 of the individual wires 7 are within the borehole 19, the individual wires 7 are not out of the borehole 19 and the individual wires 7 are only indirectly, in particular via the strand 2, connected to the anchor head 101. The strand 2, however, extends from the borehole 19 to the anchor head 101 and is secured thereto, that is, the front end 6a of the support member is in the region of a working space 21 outside the borehole 19th The anchor head 101 has a fixing part 14, for example of metal, on which the support member 100 is attached, for example, is keyed. Since only the strand 2 extends to the anchor head 101, it is only this strand 2 which is grasped by the fixing part 14. The anchor head further comprises an anchor nut 16. This anchor nut 16 is arranged on an external thread 15 of the fixing part 14. The anchor head further comprises an anchor plate 17 which is pressed by the anchor nut 16 against the rock 18. After incorporation of the borehole 19 in the rock 18, the support member 100 is inserted with the strand 2, the individual wires 7 and the spacers 8 in the wellbore 19. After insertion of the support member 100 hardenable and not yet cured mass 1 1 in the field of a borehole mouth 20 is introduced into the wellbore 19. In the process, the hardenable mass displaces air from the borehole 19. This displaced air is guided through longitudinal channels 4 between the wires 3 of the strand 2 through the strand 2 and flows at the front end 6a of the strand 2 in the working space 21 outside the borehole 19 out. When introducing the hardenable mass 1 1 in the wellbore 19, the hardenable mass 1 1 comes into direct contact with an outside 9 of the strand 2 and an outer side 10 of the individual wires 7. Thus, after hardening introduced into the wellbore 19 hardenable mass 1 1 a cohesive connection between the strand 2 and the individual wires 7 on the one hand and the rock 18 on the other hand produced (Fig. 1).

The front end 6 of the individual wires 7 lies within the borehole 19, whereas the front end 6a of the wires 3 of the strand 2 lies outside the borehole 19 in the working space 21. Between the end 6a of the wires 3 of the strand 2 and the end 6 of the individual wires 7 there is thus a front end portion 22 of the support member 100 in which a smaller number of wires 3, 7 and a smaller number of the sum of the cross-sectional area of the wires 3, 7 is given as outside the front end portion 22, for example, in the middle or at the section according to AA in Fig. 1. The fixing part 14 is only directly attached to the strand 2, so that only the strand 2 can be biased. It is only a relatively small number of wires 3 out to the fixing part 14, so that thereby the fixing part 14 can be very easily constructed.

In Fig. 3, a second embodiment of the strand anchor 1 is shown. In the following, only the differences from the first exemplary embodiment according to FIG. 1 will be described essentially. The strand anchor 1 has no individual wires 7 and no spacers 8. The wires 3 of the strand anchor 1 are thus formed exclusively by the wires 3 of the strand 2. In this case, the strand 2 has a varying number of wires 3 and / or a varying sum of cross-sectional areas of the wires 3 in the direction of the longitudinal axis 28. At a central portion 29 between the front end portion 22 and the rear end portion 23, the number of wires 3 of the strand 2 is larger than at the front end portion 22 and the rear end portion 23. A first or middle part of the wires 3 is of the outermost front end 6a of the support member 100 is guided to an outermost rear end 5a of the support member 100, so that the first part of the wires 3 is present both at the front and rear end portions 22, 23 and at the middle portion 29. A second part of the wires 3 is present only at the central portion 29, so that a front end 6 of this second part of the wires lies within the borehole 19.

In Fig. 4, the abscissa starting from the outermost front end 6a, the length s of the support member 100 is plotted on the ordinate and the tensile force received from the support member 100. The value s _m indicates the position of the borehole mouth 20 at. As can be seen from FIG. 4, the tensile forces to be absorbed by the support member 100 in the direction of the longitudinal axis 28 of the strand anchor 1 are centered on the support member 100, in the middle portion 29, largest and at end portions 22, 23 smaller.

In FIG. 5, the abscissa also shows the length s of the support member 100, starting from the outermost front end 6a of the wires 3. The ordinate represents the sum of the cross-sectional area Q of the wires 3, 7. wear. At the front and rear end portions 22, 23, the sum of the cross-sectional areas of the wires and the number of wires is smaller than at the middle portion 29. Thus, the number of wires 3, 7 is adapted to the tensile force to be absorbed by the support member 100.

6, an embodiment of the fixing part 14 is shown. The fixing member 14 comprises a sleeve member 25 and a wedge 24. The sleeve member 25 comprises a front sleeve member 26 within which the wedge 24 is disposed, and a rear sleeve member 27, on the outside of the external thread 15 is incorporated. The strand 2 of the support member 100 is passed through the wedge 24, the sleeve member 25, the anchor nut 16 and the anchor plate 17. By means of the wedge 24, a radial compressive force is applied to the strand 2, and the strand 2 is fixed to the sleeve element 25.

The internal thread of the anchor nut 16 is screwed to the external thread 15 of the rear sleeve part 27. Compressive forces from the rock 18 can thus be transferred via the armature plate 17 to the armature nut 16, from the latter to the sleeve element 25 and from this again to the strand 2. The front and rear sleeve part 26, 27 are preferably formed in one piece. The wedge 24 and the sleeve member 25 with the front and rear sleeve portion 26, 27 are preferably arranged coaxially or concentrically with the longitudinal axis 28 of the strand 2. This also applies to the anchor nut 16 and the anchor plate 17. Preferably, the wedge 24 on the outside completely or substantially completely on the strand 2, so that thereby a large contact surface between the wedge 24 and the strand 2 is present.

In a further, not shown embodiment of the fixation tion part each wire 3 is attached separately to the fixing part 14. For this purpose, the fixing part 14 has wire openings and the number of wire openings of the fixing part 14 is equal to or greater than the number of wires to be fastened with the fixing part 14. The individual wires which are guided through the wire openings can, for example, se be attached separately by transverse fasteners to the wire openings.

In the embodiment of Figure 7, the support member 100 two strands 2 and 2 ', wherein only the first strand 2 extends to the anchor head 101 and only the first strand 2 is surrounded by the anchor head 101, whereas the second strand 2' in front of the anchor head 101st ends. The two strands 2 and 2 ', which preferably have the same cross-section, are connected to one another via spacers 8. The anchor head 101 can be designed in detail as described in the previous exemplary embodiments.

Overall, significant advantages are associated with the inventive strand anchor 1. Only a first part of the wires 3 of the strand anchor 1 is guided out of the borehole 19 to the anchor head 101 and fastened thereto for prestressing the strand anchor 1. As a result, only a portion of the wires 3 is connected to the fixing part 14 and thereby the fixing part 14 structurally much simpler structure and is therefore cheaper to manufacture. A further part of the wires 3, 7 is additionally arranged within the borehole 19 and serves to absorb tensile forces during deformations of the rock 18. The number of wires 3, 7 or the sum of the cross-sectional area of the wires 3, 7 is thus advantageously adapted to the tensile forces to be absorbed by the wires 3, 7.

Claims

Strand anchor (1), in particular for use in mining, comprising

- A plurality of wires (3, 7) comprising the support member (100) and

- An anchor member (100) disposed on the anchor head (101), characterized in that only a portion of the wires (3, 7) of the support member (100) to the anchor head (101) extends, whereas the other part of the wires (3, 7 ) of

Support member (100) before the anchor head (101) ends.

Strand anchor according to claim 1, characterized in that the wires which terminate in front of the anchor head have a different surface finish and / or a different diameter than the wires which extend to the anchor head.

Strand connector according to one or more of the preceding claims, characterized in that the support member is a stranded wire (2), wherein only a portion of the wires of the strand reaches to the anchor head, whereas the other part of the wires of the strand terminates in front of the anchor head.

Strand anchor according to one or more of claims 1 or 2, characterized in that the support member consists of a central strand and a plurality of individual wires surrounding the strand at a distance, wherein the wires of the strand extend to the anchor head and the individual wires terminate in front of the anchor head.

Strand connector according to one or more of claims 1 or 2, characterized in that the support member consists of parallel individual wires, wherein only a portion of the individual wires to extends to the anchor head, whereas the other part of the individual wires ends in front of the anchor head.

Strand anchor according to one or more of claims 1 or 2,

characterized in that the support member (100) comprises two strands (2, 2 '), the first strands (2) extending to the anchor head (101), whereas the second strands (2') terminate in front of the anchor head (101).

7. Strand anchor according to one or more of the preceding claims, characterized in that the anchor head has an anchor nut (16) for biasing the support member and one of the anchor nut (16) supported anchor plate (17) for resting on the rock (18).

8. Arrangement consisting of a substrate having a borehole (19), in which a strand anchor (1) is taken up according to one or more of the preceding claims and bonded by means of a hardened mass to the substrate, wherein the hardened mass preferably to the borehole mouth of the borehole enough.

9. A method for fastening a strand anchor (1), in particular a strand anchor (1) according to one or more of the preceding claims 1 to 7, with the steps:

Incorporation of a borehole (19) in rock (18),

- introducing a plurality of wires (3, 7) comprising the support member (100) in the borehole (19),

- introducing hardenable mass (11) into the borehole (19), characterized in that the strand anchor (1) is introduced such that a front end (6a) of a first part of the wires (3, 7) outside the borehole (19 ) and a front end (6) of a second part of the wires (3, 7) within the borehole (19).